The present invention relates to removal of harmful solids, bacteria, hydrocarbons and the like from waste water such as industrial, manufacturing, municipal and agricultural waste water.
There are three basic methods and one advanced method typically used in the prior art for treating waste water prior to discharge into a sewage treatment plant or into rivers or streams, as follows:
A. Primary treatment.
Solids are mechanically separated from liquid wastes by settling and/or screening. Regardless of the ultimate disposal method it is desirable to remove, by screening, as much suspended solids as is feasible. Failure to screen out the solids results in pollutants being discharged into our rivers and streams or clogging filters if discharged to a sewage treatment plant. With this method of treatment the pH of the waste water is not altered. Thus, without further treatment, highly alkaline or acidic waste water would still enter sewage treatment plants, rivers and streams.
B. Secondary treatment.
Biological processes are used to reduce dispersed solids and the soluble organic content of liquid waste. Biological methods are most suitable for treating small volumes of waste water, usually in two stages. In the first stage, the screened water is admitted to a tank where air is continuously diffused into it. The wastes may be detained and aerated in batch or continuous flow operations. The efficiency of the process depends on building up a vigorous culture of suitable bacteria in the aeration/digestion tank. In the second stage of the process, the waste passes through sedimentation tanks where the flow is made as quiescent as possible in order to promote either flotation or settling of suspended solids. In certain situations, the suspended solids can be removed, rendering the water suitable for discharge to a sewage treatment plant or a body of water. In other cases, the water would be chemically treated to a relatively neutral pH prior to discharge in the sewage treatment plant or body of water. The cost for this method is extremely high and is generally used to treat only small volumes of waste water.
C. Spray and irrigation methods.
These methods consist of spreading the liquid waste over the surface of the ground by means of irrigation or a high pressure spray system. A rate of application is used which effects minimum damage to vegetative growth and avoids surface run-off and subsequent (or possible) erosion. These systems require large amounts of land and an actively growing crop to aid in absorption and to prevent soil erosion. Failure to properly screen waste could cause great difficulty in operation and unpleasant odors can be produced. There is a further possibility of ground water contamination unless great care is taken in selecting property for this use. During rainy seasons, the water tables typically rise, increasing the possibility of ground water contamination.
D. Advanced treatment.
More advanced methods of treating waste water, generally called tertiary treatment methods, take up where the first three methods leave off. One of these is the process known as coagulation-sedimentation. In this process, alum or lime is added to effluent as it comes from secondary treatment. The flow then passes through flocculation tanks where the chemicals cause the smaller particles to floc, or bunch together, in large masses which are removed by sedimentation. Another tertiary treatment method aims at getting rid of the dissolved refractory organic substances--stubborn organic matter which persists in water and resists normal biological treatment. By passing the effluent through a bed of activated carbon granules, more than 98 percent of the remaining dissolved organic matter can be removed by absorption. Another tertiary treatment is that of electrodialysis, by which salts from an effluent are removed from water by the action of an electric field. These methods are extremely costly and complex and would be unreasonable to use for any large quantities of water.
The U.S. Environmental Protection Agency (EPA) has issued standards for the quality of stream water and the strength of an effluent which can be legally discharged into it. The EPA is primarily a regulatory agency, with responsibilities for establishing and enforcing the environmental standards within the limits of its various statutory authorities. The agency shares many of its enforcement authorities within the states.
One of the major areas of EPA activity affecting food and processors is the Federal Water Pollution Control Act Amendment of 1972. The law created a program with three major elements: Uniform nation-wide standards, enforceable regulations, and a permanent program based on effluent limits and geared to specific chemicals, for improved physical and biological integrity of the nation's waters. Industry is required to meet the standards set up, regardless of the plant location and capacity of the stream for absorbing the wastes, without unreasonable damage. In some instances, this approach has resulted in unjust hardship to industry.
The waste water treatments of the prior art typically exhibit the following further disadvantages:
1. They are ineffective in separating out solids from waste water, with consequent contamination and clogging of filters in sewage treatment plants or direct contamination of water resources; PA1 2. They are ineffective in eliminating microorganisms from the waste water; PA1 3. They are expensive to provide in that they require large amounts of land and/or extensive structure. PA1 4. They are expensive to operate in that they require large amounts of precipitation agents or other substances which must be discarded following use; and PA1 4. They add harmful chemicals and other substances to the treated water. PA1 (a) providing a housing having an inlet and an outlet for the liquid, a cylindrical drum member rotatably mounted in the housing and having a multiplicity of passages formed between inside and outside surfaces of the drum member; PA1 (b) rotating the drum to a peripheral speed of at least 1000 feet per second; PA1 (c) feeding the liquid into the inlet and out of the outlet of the housing; and PA1 (d) inducing a recirculating flow of the liquid through the passages and in contact with the drum for separating impurities from the liquid. PA1 The step of inducing the recirculating flow can include the steps of: PA1 (a) providing a plurality of baffle blades within the drum; and PA1 (b) moving the baffle blades for producing an outward flow near one end of the drum and having a flow component toward the opposite end of the drum, and for producing an outward flow near the opposite end of the drum and having a flow component toward the one end of the drum.
Thus there is a need for a waste water treatment in which the solids are entirely removed prior to discharge, producing a neutral pH of the waste water prior to discharge; that does not require holding or settling tanks; that is a high speed process operating at whatever speed is required under various conditions; that does not require large amounts of land; that does not add additives or chemicals to the water at any time; that has low maintenance and operating costs; that eliminates land erosion; and that provides an environmentally safe process for preventing the polluting of underground water supplies, rivers and streams.